Sarah Russell (asker) Nov 14, 2019:

Thanks very much for your suggestions so far. On the basis of Wolf's suggestion, I have come up with 'tax enhancement measures'. I also agree with Daryo that more context is required, so will ask the client for clarification when submitting the translation.

Daryo Nov 13, 2019:

without far more context only wild guesses are possible.

We have no ides what kind of "risks" related to "fiscal" they are talking about, nor what exactly is supposed to be "optimised" by these "clés d'optimisation".

You could simply use "optimization / optimizing keys" without losing any sleep about the exact meaning of it, but then you'll hit the same wall again with "sécurisation" - what would be the exact meaning of that? Put in secure place or "securing" = obtaining?

I see so far 4 possible meanings, but none of them with any obvious link to "fiscal".

Any more clues?

Wolf Draeger Nov 13, 2019:

Tax avoidance/reduction Optimisation fiscale is finding (very creative) ways to pay less tax or, more politely, lower the tax burden. Clés is just a gimmick meaning strategies and mechanisms.

I'll be happy to post an answer, but I think this question belongs under Business/Finance where others in the field can also have a go.